In a wireless cellular communication system, when a terminal in the system executes no service or fewer services, the terminal may usually enter a Discontinuous Reception (DRX) time period. Usually, the DRX time period is divided into two time periods: an active time period and a sleep time period, as shown in FIG. 1. The terminal may turn off most of internal operation units when entering the sleep time period. The operation unit includes a system clock which may also be called as a high-frequency clock. At this point, the terminal turns off the high-frequency clock and adopts a low-frequency clock with a lower frequency and lower power consumption to maintain system timing. For example, most of terminals in the wireless cellular communication system usually maintain system timing by adopting low-frequency clocks with a frequency of 32.768 kHz. When entering the active time period, the terminal recovers the system timing through the low-frequency clock in the sleep time period at first, and converts the low-frequency clock into a high-frequency clock through multiplying the low-frequency clock by a calibration factor, so as to recover the system timing. Since the low-frequency clock has relatively lower accuracy and stability and cannot perform temperature compensation, the low-frequency clock may be influenced by a factor such as an environment and a temperature. After the terminal recovers the system timing, the system timing may have a calibration deviation, and the terminal further performs frequency and time synchronization, and then may initiate or receive paging. It can be seen that the terminal should regulate the calibration factor to make the recovered system timing more accurate, thereby improving execution efficiency of a subsequent synchronization operation.
In an existing calibration factor regulation manner, a system clock (high-frequency clock) is usually adopted as a calibration clock, to calibrate a low-frequency clock. That is, the high-frequency clock and the low-frequency clock operate simultaneously and count respectively, and after a time period, a ratio of the high-frequency clock to the low-frequency clock is calculated to obtain a calibration factor. However, the high-frequency clock may be influenced by clock jitter. Therefore, the existing calibration factor regulation manner should increase a calibration time to ensure calibration accuracy. The higher the calibration accuracy is, the longer the calibration time is. Usually, the calibration time should be more than 100 ms. However, an excessively long calibration time may reduce a sleep time of a terminal in the sleep time period, which may increase standby power consumption of the terminal.